Multiple-walled arc-quenching chamber for vacuum switching devices

ABSTRACT

The insulating portion of the housing of an arc-quenching chamber is created in the form of a double-wall cylinder. To reduce the permeability of the chamber to gas, the hollow space between the walls is filled with gas at a pressure which is higher than that in the evacuated chamber but lower than the atmospheric pressure.

United States Patent Inventors Alired G. H. Gotsch Berlin-Kopenick; Heinz Hanisch, Berlin-Friedrichshagen; Ernst Freund, Berlin-Friedrichshagen, all of, Germany Appl. No. 822,939

Filed May 8, 1969 Patented Aug. 3, 1971 Assignee Instltut Prufleld Fur Elektrische Hochleistungstechnik BerIin-Lichtenberg, Germany MULTIPLE-WALLED ARC-QUENCHING CHAMBER FOR VACUUM SWITCHING DEVICES 9 Claims, 4 Drawing Figs.

u.s.c|. 200/144 3,

v 174/1105, 313/26 m. a. ..no1h 33/66 Field ofSearch zoo/144.2,

[56] References Cited UNITED STATES PATENTS 344,343 6/1886 Buell 313/26 X 2,160,081 5/1939 Niclassen 313/26 X 3,236,978 2/1966 Lester 200/144 (.2) 3,268,696 8/1966 Lindell 200/144 (.2)

FOREIGN PATENTS 1,245,472 7/1967 Germany..... 200/144 (.2)

Primary Examiner- Robert K. Schaefer Assistant Examiner-Robert A Vanderhye Auomey-Nolte and Nolte ABSTRACT: The insulating portion of the housing of an arcquenching chamber is created in the form of a double-wall cylinder. To reduce the permeability of the chamber to gas, the hollow space between the walls is filled with gas at a pressure which is higher than that in the evacuated chamber but lower than the atmospheric pressure.

FIG. 4

INVENIORS ALFRED CfOTSCH HEINZ HAN/SCH ERNST FREUND By ATTORNEYS PATENTEU AUG 3197i F/Gl FIGZ

MULTIPLE-WALLED ARC-QUENCIIING CHAMBER FOR VACUUM SWITCHING DEVICES The present invention relates generally to arc-quenching chambers for vacuum switching devices.

In particular, the present invention relates to the reduction of permeation to gas in the housing of such chambers.

Conventional housing for arc-quenching chambers wherein switching electrodes and shielding members are disposed are made up of metal and glass, or of metal and ceramic. Usually, the housing is designed in the form of a cylinder the cylindrical wall portion of which is of glass or ceramic and hermetically sealed by a special bonding process to metal closure plates.

The interior of the arc-quenching chamber is usually highly evacuated and, from the outside, the walls of the housing are exposed to normal atmospheric pressure.

The disadvantage of such known structures resides in that due to relatively long spark-over paths or tracking spark-over paths, the dimensions of the housing must be correspondingly increased and the resulting extended insulating surfaces secured against the penetration of gases into the interior of the chamber. Consequently, special glasses or high quality ceramic material must be employed to avoid an efiective permeability to gases.

The primary object of the present invention is to provide an arc-quenching chamber for vacuum switching devices the housing of which is almost completely impermeable to gases and reduced in size, especially in total height.

In particular, the object of the present invention is to design a housing in which the surface portions which are susceptible to the penetration by gas are reduced.

Another object of the present invention is to reduce or remove the danger of penetration of gases into the interior of the evacuated arcquenching chamber.

A further object of the present invention is to provide an arc-quenching chamber which--in spite of lower height in comparison with conventional chambers-4s adjustable to operate at different nominal voltages and adaptable to installation in outdoor or indoor stations.

According to the present invention, the above objects are attained so that the housing of a vacuum arc-quenching chamber which is made at least partially of insulating material, has the insulating portion carried out as a multiplewall, preferably two-wall envelope with one or more hermetically sealed hollow spaces between the walls. The hollow spaces are adapted for being evacuated, and are filled with gas, such as, for example, air, inert gas or SF The pressure of the gas in the hollow space is higher than the extremely low pressure in the interior of the evacuated chamber but lower than normal atmospheric pressure.

In a preferred embodiment of the invention, the double-wall housing section consists of an outer insulating cylinder and of a concentrically arranged inner cylinder of insulating material. The resulting hollow space therebetween is hermetically sealed. v

To enable the application of like arc-quenching chambers for different nominal voltages in a switching device, the double-wall housing consists, according to another variation of the present invention, of an inner insulating cylinder and of an insulating outer wall surrounding the latter.

The outer wall which can be assembled of several parts is dimensioned and designed in such a manner as to ensure the required spark-over paths or tracking spark-over paths between two voltage-carrying closure plates arranged on the ends of the inner cylinder, and to maintain a fixed height of the housing of the chamber for various nominal voltages as well as for the employment thereof indoor and indoor stations.

In an-especially advantageous modification of the present invention, the double-wall housing is in the form of a homogenous outer insulation cylinder coupled at the ends thereof .with an inner cylinder which is assembled of two portions, namely of insulation cylinder portions and of a metal cylinder portion. in this embodiment, the insulating surface area of the inner cylinder which has the greatest permeability to gas, is most efi'ectively reduced.

The multiple-wall housing can be also assembled of one of more metal cylinder and insulation cylinder sections, the latter sections having double walls and being integral with the ends of the former metal sections. It is also advantageous to arrange one or more of these metal cylinder sections in a certain distance around the contact surfaces of the switching electrodes to serve as shields against metal vapors. Of course, it is possible to equip these shielding metal cylinder sections with additional, inwardly projecting shield elements.

According to another feature of the present invention, the portions of the housing which are made up of insulating material are joined one to another either directly, for example by casting, melting, etc., or by means of fasteners or connecting members.

Within the hollow space between the two walls of the housing, the potential and drive-controlling parts, such as resistors, condensers, rectifiers, spark gaps and the like, can be arranged for being protected from the outer atmosphere, especially from the extremely changeable humidity and coating effects.

To eliminate dissipative heat, it can be useful, in some applications, to create separate cooling channels on the doublewall housing, disregarding the fact that some of the design advantages of this invention may be partially diminished.

The arc-quenching chamber according to the present invention is primarily characterized in that the degree of susceptibility to permeation of its housing by gas is substantially reduced. This favorable feature results from the fact that the walls of the insulating section of the housing are doubled and the gas pressure in the intermediate hollow space is set to be between the low pressure in the interior of the chamber and the atmospheric pressure. The pressure difference at each side of the two walls of insulating material, is, advantageously, made several orders of magnitude smaller than the total pressure difference between the inside of the arc-quenching chamber and the outside.

Since the aforementioned pressure differences determined the active force for the gas penetration, the permeation to gas in each of the walls is accordingly decreased. For this reason, the rate of the pressure increase within the chamber and in the intermediate space is in comparison with single-wall housings substantially slowed down.

It will also be noted that due to metal structure of the inner wall section which, simultaneously, serves as a shield, the susceptibility of the inner wall to the gas penetration is further reduced and, therefore, the permeability to gas of the entire device. The latter reduction can be carried out to a considerable extent since the spark-over strength resistance of the remaining insulating paths on the inner wall is much greater in vacuum than in the air.

Still further advantage of the present invention results from that high quality special glass or ceramic material is not necessary for the housing, and it is possible to employ much cheaper kind of glass or ceramic material and thus considerably reduce the price of the arc-quenching chambers.

The inventive solution also enables to reduce the dimensions of the housing and to create favorable conditions for the design of a series of standardized models, since by maintaining a constant height of the housing it is possible simply by shaping and suitable dimensioning of the other surface area of the housing to accommodate the arc-quenching chamber for the operation at different nominal voltages as well as to modify the same for outdoor or indoor applications.

In order that the present invention may be readily carried into effect it will now be described by way of an example in the following description, with reference to the accompanying drawings, wherein,

FIGS. 1-4 show, in partially sectional views, side elevations of four various modifications of the arc-quenching chamber according to the present invention.

The arc-quenching chambers of this invention as shown in FIGS. 1-4 have the same basic structure. However, as regards to the housing, they differ one from another in design.

Referring now to FIG. 1, the arc-quenching chamber 1 comprises cylindrical housing la, lb of insulating material ter minated at each end thereof with metal closure plates 3 and 4, and evacuated. Lower closure plate 3 supports fixedly mounted contact electrode whereas the upper closure plate serves as a guide for movable contact electrode 6. The movable electrode is sealed by means of metal bellows 7 which is secured at one end to the closure plate 4 and at the other end to stem 6a of electrode 6. This arrangement enables that the spaced contact surfaces of electrodes 5 and 6 can move for performing the switching function. In the area of contact surfaces of electrodes 5 and 6, there is disposed shield member 8 which protects the insulating inside wall of housing 1 from metal vapors generated by the current interruption and ensures that the insulation between the closure plates and the electrodes remain unaffected.

According to one feature of the present invention, at least the section of housing 1 which is made of insulating material, is in the form of two spaced concentrical walls la and 1b with hermetically sealed hollow spaced 9 therebetween. The hollow space 9 contains air and/or another gas such as, for example, inert gas or SP The pressure of the gas is higher than that in the interior of the arc-quenching chamber but lower than normal atmospheric pressure. In the embodiment of the arc-quenching chamber of this invention as shown in FIG. 1, the double-wall housing is created of outer insulation cylinder la and of a concentrically arranged inner insulation cylinder lb. The two cylinders are spaced one from another and hermetically sealed at their end portions to form the intermediate hollow space 9.

FIG. 2 shows another variation of the present invention. Double-wall housing 1 comprises inner insulating cylinder lb and homogenous outer envelope la which completely surrounds the outer surface of the inner cylinder and is coupled thereto by means of connecting members 10 sealing the resulting intermediate space 9. The outer wall ofenvelope la is provided with ribs la to improve insulating condition in the space or surface spark-over path between the voltage carrying closure plates 3 and 4. This embodiment ofthe housing is particularly adequate for the production of standardized series of the chambers since the configuration of the inner cylinder lb remains unchanged whereas, only by means of an adequate shaping and dimensioning of the outer envelope la, the arcquenching chamber can be adjusted to various operating voltages or for the application in outdoor or indoor stations.

FIG. 3 illustrates another modification of chamber 1 with the housing having homogenous outer insulation cylinder la and an inner cylinder assembled of three superimposed sections, namely of two insulating cylinder sections lb and an intermediate metal cylinder section lb. The sections are firmly coupled one to another and by means of connecting members 10' hermetically sealed to the end areas of cylinder la. [mermediate metal cylinder lb which encircles at a certain distance the contact surfaces of electrodes 5 and 6, works as a metal shielding, thus making additional shield elements unnecessary.

Moreover, due to the employment of the intermediate metal cylinder section, the insulating area of the inner cylinder which is susceptible to the gas penetration becomes reduced to minimum, whereby the permeation of gas into the entire chamber is effectively suppressed.

Since the insulating cylinder sections contact a well-insulating vacuum at one side and a low-pressure intermediate space at the other side, the height of these insulating cylinder sections can be reduced to much greater extent than it is shown in H6. 3.

FIG. 4 shows an arc-quenching chamber wherein the housing is formed by an intermediate metal cylinder section la connected at each end thereof with double-walled insulation cylinder sections 1a", 1b. In the shown embodiment, the intermedrate metal cylinder portion [5 provided with inwardly projecting shield elements 11 preventing metal vapors from impinging against the insulating cylinder sections lb.

It is also possible to create double-wall closure plates of insulating material whereas a single-wall cylindrical envelope is made of metal to serve as shielding.

What we claim is:

1. In a vacuum are arc-quenching chamber, wherein a first switch electrode is rigidly mounted on a first metallic, electrically conductive structure, and a second switch electrode is movably mounted on a second metallic, electrically conductive structure, for motion of the second toward the'first electrode and away from it, said structures having rigid plates to close opposite ends of a highly evacuated arc chamber, the improvement which comprises: a plurality of rigid, electrically insulative, mutually surrounding wall structures, having ends hermetically sealed to one another, and to the outer edges of said plates, to provide a sealed jacket space; and a rarified medium, at higher but subatmospheric pressure, in said jacket space.

2. The combination of claim 1 wherein the electrically insulative wall structures are of ceramic material.

3. The combination of claim 1 wherein the electrically insulative wall structures comprise a pair of short cylinders, radially closed spaced from one another.

4. The combination of claim 1 wherein the outermost, electrically insulative wall structure has ribs thereon to add to the spark-over path or tracking spark-over path provided by the insulative wall structure.

5. The combination of claim 1 additionally including: metallic wall structure which, longitudinally of the arc chamber, is spaced from said plates and spaces path of the mutually surrounding electrically insulative wall structures from one another.

6. The combination of claim 5 wherein the metallic wall structure is of single-wall type and does not provide a jacket.

7. The combination according to claim 6 wherein the metallic wall structure is arranged to provide shielding around the electrodes.

8. The combination according to claim 1 wherein the rarified medium in the jacket space is selected from the group consisting of air, inert gas and SF 9. The combination according to claim 1 wherein said pressure of the rarified medium in the jacket space differs by several orders of magnitude from the pressures inside the arcquenching chamber and on the outside. 

1. In a vacuum are arc-quenching chamber, wherein a first switch electrode is rigidly mounted on a first metallic, electrically conductive structure, and a second switch electrode is movably mounted on a second metallic, electrically conductive structure, for motion of the second toward the first electrode and away from it, said structures having rigid plates to close opposite ends of a highly evacuated arc chamber, the improvement which comprises: a plurality of rigid, electrically insulative, mutually surrounding wall structures, having ends hermetically sealed to one another, and to the outer edges of said plates, to provide a sealed jacket space; and a rarified medium, at higher but subatmospheric pressure, in said jacket space.
 2. The combination of claim 1 wherein the electrically insulative wall structures are of ceramic material.
 3. The combination of claim 1 wherein the electrically insulative wall structures comprise a pair of short cylinders, radially closed spaced from one another.
 4. The combination of claim 1 wherein the outermost, electrically insulative wall structure has ribs thereon to add to the spark-over path or tracking spark-over path provided by the insulative wall structure.
 5. The combination of claim 1 additionally including: metallic wall structure which, longitudinally of the arc chamber, is spaced from said plates and spaces path of the mutually surrounding electrically insulative wall structures from one another.
 6. The combination of claim 5 wherein the metallic wall structure is of single-wall type and does not provide a jacket.
 7. The combination according to claim 6 wherein the metallic wall structure is arranged to provide shielding around the electrodes.
 8. The combination according to claim 1 wherein the rarified medium in the jacket space is selected from the group consisting of air, inert gas and SF6.
 9. The combination according to claim 1 wherein said pressure of the rarified medium in the jacket space differs by several orders of magnitude from the pressures inside the arc-quenching chamber and on the outside. 